Probably easiest to buy the required paper ticket at the London Waterloo Main Line Rail Ticket Office
You need a RETURN ticket from “London Boundary Zone 6” to Woking
There are various Return tickets
Off Peak Day Return if leaving Waterloo after 9:00 – probably 09:30 is the first sensible train. But you can leave as early as you wish on Saturdays. £10.00
If you are leaving after around 11:40, then it is the much cheaper Evening Out Return. £7.30. Yes evenings start early
On Sunday, it is the Sunday Out Return. Leave as early as you wish. £7.30
If you have a railcard, say Senior Railcard, then ask for the Railcard discount, and Mondays to Fridays the first available train is 09.30
And as you are using the Oyster 60+, you can use non stop trains
You will not tap out at Woking as you will use the paper ticket. Likewise you do not tap in at Woking on the way back
The Oyster 60+ will not care that you tapped in at Waterloo and did not tap out. Likewise when you tap out when you get back to Waterloo